Yes, you can upload fonts as long as you have the proper licensing for them. Many fonts require special licensing (a server/product creation license, which is different than a commercial license) in order to be used on design platforms like ours, where customers can use a font they have not purchased.
To upload fonts to your Corjl account, open a design and then click on the Fonts tab, then click on the Upload button:
You will then be prompted to upload your own fonts. These fonts will be visible in the My Fonts area of your account.